fix javadoc warning

src/main/java/com/imyeyu/spring/service/AbstractEntityService.java

@@ -20,7 +20,17 @@ public abstract class AbstractEntityService<T, P> implements BaseService<T, P> {
 	/** 基本 Mapper */
 	protected BaseMapper<T, P> baseMapper;
 
-	/** @return Mapper 实例 */
+	/**
+	 * 创建实体服务
+	 */
+	protected AbstractEntityService() {
+	}
+
+	/**
+	 * 获取 Mapper 实例
+	 *
+	 * @return Mapper 实例
+	 */
 	protected abstract BaseMapper<T, P> mapper();
 
 	/** 检查 mapper */